In many types of equipment, such as in pumps, it is desirable to reciprocate a piston through a cylinder to perform work. The piston is connected to a piston rod which in turn is connected to a cross-head rod by a suitable joint. The cross-rod is driven by a motor driven crank and is mounted in guides so that it reciprocates along a longitudinal axis. In such type of equipment, it is essential that the piston runs true so as to avoid excessive wear. This is particularly so where the cylinder of the equipment has a ceramic liner. Pumps having ceramic cylinder liners have superior abrasion and corrosion resistance compared to conventional metal cylinder liners. However, even minor misalignment problems between the ceramic cylinder liner and the pump's metal piston can cause excessive abrasion of the ceramic cylinder liner and result in a substantial reduction in the life of the ceramic cylinder liner. The misalignment can result from angular offset between the reciprocal axis of the piston rod relative to the cross-head rod or lateral offset in that the reciprocal axis of the piston rod is parallel to but laterally offset from the reciprocal axis of the cross-head rod. One solution to this problem is set forth in U.S. Pat. No. 2,639,172 to Leonard, Jr., wherein a cavity is formed between one end of a piston rod and the associated end of a cross-head rod. The cavity is filled with a fluid and is sealed by a bellows. One of the problems associated with equipment disclosed in Leonard, Jr., as set forth in column 4, lines 21-39, is that it is not suitable for use in transmitting large forces. Also, the structure in Leonard, Jr. is designed so that any misalignment results in movement of the plunger.